The present invention is generally related to position sensors, and, more particularly, to a linear position sensor that uses a relatively small magnet relative to the sensing range of the sensor.
Angular and linear position sensors are widely used in automatic control systems as feedback-sensing devices in one or more control loops of the system. In the automotive industry a relatively recent trend is providing control-by-wire in lieu of the more traditional control provided by mechanical linkages, such as cables, rods, etc.
Lower cost, higher performance, and utilization of robust sensing technology are some of the factors that make control-by-wire systems attractive to suppliers of automotive equipment, such as the assignee of the present invention. However, these control-by-wire systems generally require more sensors to provide the appropriate control functionality. Examples of sensors that are needed include sensors for providing linear position measurements. Although there are several technologies available for linear position measurement, these technologies may somewhat fall short in meeting the ever-increasing demands that are necessary to successfully compete in the automotive industry. Examples of such demands include lower costs, lower weight and volume as well as higher reliability and performance.
There are some known sensor design arrangements that use a magnet as the moving part relative to a stationary linear Hall device. Unfortunately, such known arrangements require that at least one of the magnet dimensions (e.g., magnet length) be larger than the measuring range of the sensor. This type of arrangement causes the sensor cost to increase because of the relatively high cost of the magnet, particularly for applications that require a relatively large measurement range.
In view of the foregoing, it would be desirable to provide an improved magnetic circuit that is not subject to the dimensional constraints of existing sensor arrangements while providing a relatively large linear output range. It would be further desirable to incrementally reduce the sensor costs by utilizing a relatively small magnet.